Note: Descriptions are shown in the official language in which they were submitted.
,
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PA 8105
PROCESS FOR THE PRODUCTION OF ELONGATED PROFILES OR LEDGES
OUT OF SOLIDIFYING MOLDING COMPOUNDS IN A MOLD AND MOLD
A method for the production of elongated profiles or ledges out of solidifying
compounds in a mold with at least one lower part and at least one upper part,
the
molding compound being continuously injected into the mold cavity, wherein the
injected compound is transported away from the gating point(s) and out of the
mold
under steady extension of the mold cavity and under steady elongation of the
forming profile or ledge by relative movement of mold components and wherein
molding compound is injected until the profile reaches its pre-defined length.
Furthermore a mold for the production of elongated profiles or ledges out of
solidifying molding compounds with at least one lower part and one upper part,
wherein at one of the parts of the mold a gating insert is located and at the
other a
profiled mold insert is located that determines the geometry of the profile or
ledge at
least to a large extend and that is a part of the mold cavity, wherein the
profiled mold
insert and the part of the mold comprising the gating insert can be moved
relatively
to each other in direction of the longitudinal axis of the mold such that by
this
movement the profile or ledge can be produced inside and outside of the mold
in the
designated length.
A process and a device of the herein before mentioned type are known from WO-A-
2006/045720. There a cavity formed between mold components of the upper and
the lower mold part is filled with moulding compound, after initial filling of
the cavity
and under continued injection of new molding compound the injected molding
compound is steadily transported away and out of the mold under extension of
the
shaping area and under extension of the profile to be formed.
,
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It is representative for the known process and the know mold that after
volumetrical
filling of the initial cavity the resulting molding part steadily grows or is
steadily
formed, respectively, directly at the gating point of the cavity and not at
the melt front
as it is the case at conventional injection molding.
During the injection process the injected and slowly solidifying molding
compound,
that forms the profile is steadily transported away from the gating area. The
process
distinguishes from a conventional extrusion process mainly by the possibility
to
manufacture profiles of a designated length whose geometries are not that
restricted
as at a conventional extrusion process.
The US Patent No. 3,992,503 illustrates a method for the production of ribbed
tube
out of thermoplastic material. There a section of a tube is produced in an
injection
molding process in a mold cavity formed by two halves of a so that the desired
ribbing is formed on the outer surface of the tube. After solidification of
the tube
section, the outer part of the mold is removed and the set tube section is
shifted in
longitudinal direction. Then the outer part of the mold is re-positioned such
that a
mold cavity for molding the next section of the tube is formed in a closed
position.
The process steps are repeated until the tube reaches the desired length. A
further
similar process for the production of tubular components in sections, which is
based
on a similar method, is known from EP 0 018 044 Al.
The primary task of the present invention is, to further improve the process
known
from WO-A-2006/0405720 and the known mold, especially to manufacture
particularly high quality profiles and ledges of a designated length.
As far as the method is concerned, these and other objects of the present
invention
are attained in such a way that at the beginning of the injection an end
section of the
mold cavity, that is closed in the direction the resulting profile or ledge is
transported
out of the mold, is filled up by the molding compound beyond the gating point,
wherein, while there is relative movement of the mold components, the flow
front of
the molding compound due to the process pressure remains as a free front
section
in position compared to the upper part of the mold, wherein the mold cavity is
filled
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up while molding compound is transported away from the gating point and out of
the
mold.
According to an aspect of the present invention, there is provided a method
for
forming elongated profiles or ledges out of solidifying molding compounds by
the
means of a mold with at least one lower and at least one upper part of the
mold,
with molding compound steadily injected into a cavity, with the injected
molding
compound transported away from the gating point(s) and out of the mold,
respectively, under proceeding continued elongation of the formed profile or
the
formed ledge by relative movement of mold components and wherein molding
compound is injected until the profile or ledge reaches its designated length,
characterized in that
at the beginning of the injection process the molding compound fills up an end
section of the cavity of the profile or ledge to be formed, said end section
closed
in direction of the exit of the profile, beyond the gating point, wherein
beyond the
gating point due to the process pressure the front section of the molding
compound during the relative movement of the mold components remains in
position in relation to the upper part of the mold, as free front section of
the
molding compound, wherein the mold cavity is filled up while molding compound
is transported away from the gating point and out of the mold.
As far as the mold is concerned, the objectives of the present invention are
attained
in such a way that the profiled mold insert possesses a length that
corresponds to
the length of the profile or ledge to be manufactured and together with the
mold part
comprising the gating insert only at the beginning and at the end of the
injection
process forms closed cavity sections.
According to an aspect of the invention, there is provided a mold for the
production of elongated profiles or ledges out of solidifying molding
compounds
with at least one upper part of the mold and at least one lower part of the
mold,
wherein at one part of the mold at least one gating insert is attached and at
the
other part of the mold a profiled mold insert is attached which determines the
geometry of the profile or ledge at least to a large extent and which is a
part of
the cavity, wherein the profiled mold insert and the part of the mold
comprising
the gating insert are moveable relatively to each other in direction of the
longitudinal axis of the cavity such that due to the movement the profile or
the
ledge can be manufactured inside and outside the mold in the designated
length,
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characterized in that
the profiled mold insert comprises a cavity that corresponds to the length of
the
profile or ledge to be produced and together with the mold part comprising the
gating insert only at the beginning and at the end of the injection process
forms
closed cavity end sections.
At the process according to the invention and with the device in accordance
with the
invention at the beginning of the injection process only the frontal end
section of the
cavity is filled, at the second end section the mold cavity initially remains
open.
During the injection process the free melt front remains in position in
relation to the
upper part of the mold. The rear end section of the cavity is filled not until
the end of
the injection process. Due to the free melt front it is possible to produce
particularly
high quality profiles and ledges.
At a preferred and a particularly advantageous embodiment of the invention the
free
front section of the injected molding compound is separately tempered. This
measure allows to keep the free front section of the molding compound on a
temperature level that ensures proper flowing of the molding compound away
from
the gating point and such the generation of particularly high quality
profiles.
The free front section of the injected molding compound can be tempered in a
constant manner or variably which would particularly advantageous affect the
quality
of the profile or ledge.
In the mold part comprising the gating insert the mold in accordance with the
invention contains a tempering element that gets in contact with the injected
molding
compound and thus provides a constant or variable tempering of the free front
section of the injected molding compound. The tempering element preferably
extends on both sides of the gating point and can be cooled in front of the
gating
point in order to support the solidifying process of the profile or ledge
being
transferred out of the mold.
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In order to be able to manufacture profiles or ledges of defined lengths in a
mold it
can be considered as advantageous if the profiled mold part comprises a
movably
supported carriage comprising a profiled insert with a single-part or multi-
part
design.
Furthermore at the area where the resulting profile or the resulting ledge
exits the
mold the mold can contain a unit for aftertreatment, especially for smoothing,
of the
free surface of the profile or ledge being transported out of the mold. This
after-
treatment can be realized in different ways for example with infra-red
radiation, ultra
sonic treatment, flame treatment or mechanical finishing.
Moreover the invention relates to a component, especially a profile or a
ledge, which
is manufactured applying a process in accordance with one or more of the
process
claims
Additional design features, advantages and details of the invention will now
be
described, by the way of example, with reference to the accompanying drawing
wherein
Fig. 1 is a longitudinal cross sectional view of an injection mold in
accordance with
the present invention,
Fig. 2 to Fig. 7 are longitudinal cross sectional views in analogy to that
shown in
Fig.1 at different stages of the injection process and of the manufacturing of
a profile
or ledge, respectively.
Fig. 8 is a cross sectional view taken about on line A-A of Fig. 4,
The mold in accordance with the invention consists of a first or upper part of
the
mold and a second or lower part of the mold, which mold parts are moveable
away
from each other and towards each other in order to open and close the mold.
The
upper part of the mold comprises a mold insert 1, which is in a manner not
shown,
mounted at a fixing plate or similar of the upper mold part. A hot runner
nozzle
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extends through the mold insert 1 followed by a gating insert 3 from which the
molding compound deliverable by a injection unit 6 exits into the mold cavity
4 which
will later be described in detail. The unit 6 can be an injection unit of a
injection
molding machine or a processing unit of an extruder. The gating insert and the
end
5 section of the hot runner nozzle 2 related to it are positioned in a
central opening 7c
of a tempering element 7 positioned in a flat recess of the mold insert 1. In
the
described implementation the tempering element 7 is designed as a multipart
plate
said insert tightly fit into the recess 5 wherein its flat outer surface 7a
which is
directed against the lower part of the mold and together with the flat outer
surface 3a
of the gating insert 3 forms the boundary the mold cavity 4. The multipart
tempering
element 7 comprises a part 7d that can be cooled in front of the gating insert
and a
part that is able to be heated or cooled behind the gating insert, which is
symbolized
by the heating element 9 shown in the figures. The gating insert 3 and the
part 7d of
the tempering element 7 are designed as combined extrusion die with
calibration
zone, wherein the gating insert 3 preferably has the function of the extrusion
die
while the part 7d preferably implements the function of the calibration unit.
As described more detailed later elongated profiles or ledges are manufactured
with
the process in accordance with the invention, wherein at the beginning of the
injection process with the mold in closed position the molding compound enters
a
closed end section 4a of the mold cavity generated inside the mold, that
passes into
a elongated mold section 4b, corresponding to the length of the profile or
ledge to be
produced, said elongated section being outside the upper mold part and the
upper
mold insert 1, respectively. At the beginning of the injection process, with
the mold
just closed, the closed end section 4a is positioned just before the gating
insert 3.
The lower part of the mold comprises a profiled mold insert, which in the
implementation described above, comprises an elongated carriage 10 supported
movably in its longitudinal direction at a mold plate not shown in the figure
or similar,
the carriage having a longitudinal recess 10a in which contains an also
longitudinal
carriage insert 11. The carriage insert 11 determines the geometrical shape of
the
resulting profile or the resulting ledge 21, respectively and together with
the carriage
10, the tempering element 7 and the gating insert 3 forms the boundary of the
the
closed end section 4a of the mold cavity 4. Beyond the end section 4a the
carriage
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insert 11 together with the carriage 10 forms the longitudinal cavity section
4b, that
is open on its upper side. As Fig.1, Fig 7 and Fig. 8 show at the
implementation
described a profile or a ledge, e.g. a long, straight ledge with end caps and
a U-
shaped cross section, is formed by the design of the geometry of the single
parts,
especially the carriage insert 11 and the carriage 10. Recesses 12a (Fig. 1)
and 12b
(Fig. 5) at the end sections of the carriage inset 11 are designated for the
formation
of the end caps and connect L-shaped voids 12c (Fig. 8) which are formed
between
the carriage 10 and the insert 11 and which form the side sections of the
profile and
the ledge 21, respectively. Additional recesses 12d allow the generation of
ribs or
cross beams 21a at the profile or the ledge, respectively. As shown in Fig. 8
the
carriage insert 11 comprises jaws 11a, which are kept in position by the
clamping
force applied, so that the cavity is geometrically fixed during the injection
process in
order to accommodate the cavity pressure. Alternatively an embodiment of the
invention can be described where the jaws 11a are not fixed by the clamping
pressure over the supporting sliding elements 18 but the jaws 11a are latched
in the
carriage insert 11. In accordance with the state of the art this latching can
be done
applying mechanical, hydraulic or pneumatic latching devices. A latching of
the jaws
lla in the carriage insert 11 as described is particularly reasonable and
necessary if
the mold for the process in accordance with the invention is indented as an
extrusion die for a use in combination with an extruder.
Next to the tempering element 7 at the implementation described an after
treatment
unit 17 is integrated. As Fig. 8 shows there are sliding elements 18 operative
between the carriage insert 11 and the mold insert 1, that enable a relative
movement between the carriage insert 11 and the mold insert 1 even if there is
clamping pressure applied. The sliding elements 18 can be carried out as
massive
elements with or without anti-friction coatings as ball bearings, roller-
bearing or
needle bearings or suchlike.
In the mold insert 1, the tempering element 7, the gating insert 3 as well as
the
carriage insert 11 in each case there are drillings 22 which are intended to
convey a
tempering medium, especially a cooling medium.
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For the movement of the carriage 10 in the direction of the arrow P in Fig. 1
a linear
drive not shown in the figure can be designated, being operable electrically,
mechanically, pneumatically or hydraulically according to the state of the
art.
The tempering element 7 is of particular relevance for the quality of the
surface of
the resulting profile or the ledge to be produced 21 being in contact with the
tempering element. The heatable part 7b of the tempering element 7 behind the
gating insert 3 facilitates keeping the molding compound at a temperature
level just
slightly below the injection temperature. It can be considered as particularly
advantageous to be able to variably temper the part 7b of the tempering
element 7
during the injection sequence. The part 7d of the tempering element 7 which is
prior
to the gating insert 7 can be kept relatively cool.
Fig 1 shows the already closed mold directly before the beginning of the
injection
sequence. The carriage 10 with the carriage insert 11 is in its initial
position, the
gating point is near the frontal end of the cavity 4. The carriage 10, the
carriage
insert11, the tempering element 7 and the gating insert 3 form the boundary of
the
closed end section 4a of the mold cavity 4.
Fig. 2 shows the begin of the injection sequence, The injection unit 6 is
attached to
the hot runner nozzle 2, plastified molding compound 20 already has been
injected
into the section 4a. The gating insert is tempered such that a solidification
of the
molding compound during the filling process is prevented.
In a first step the section 4a is totally filled, with the molding compound
finally
advancing to the heated part 7b of the tempering element 7. In doing so the
molding
compound builds up a certain counter pressure to the injection pressure. The
injection pressure is set up in such a way that at the part 7b of the
tempering
element 7 a free melt front 20a emerges which in and against the direction of
translation of the carriage 10 cannot advance beyond the extension of the
tempering
element 7. Then the translation of the carriage 10 in the direction of the
arrow P
(Fig. 1 to Fig 5) is started.
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Fig. 3 shows a next stage during the continuous process of injection of
molding
compound 20. The free volume in the cavity 4 generated during the translation
of
the carriage 10 is steadily filled by the molding compound 20, said molding
compound steadily flowing in. The process pressure is kept on a constant level
causing the position of the melt front 20 underneath the heated part 7b of the
tempering element 7 to stay at least substantially constant. That way a pseudo
steady filling condition is reached.
As already mentioned the temperature at the tempering element 7 is kept on a
level
that keeps the molding compound 20 above solidification temperature in order
to
prevent a solidification during the filling stage. The molding compound 20
that is moved away from the gating point by the carriage 10 leaves the closed
section 4a and is cooled in the cooled pat 7d of the tempering element 7. The
profile
or ledge 21, that together with the carriage 10 continuously leaves the mold
is after-
treated by the after-treatment unit 17 at its free surface in order to assure
the
required quality of the resulting profile or the resulting ledge 21.
This after-treatment can include a treatment with infrared radiation, ultra
sonic
waves, flame treatment, laser radiation or similar. Also a mechanical after-
treatment
is possible by planning, sanding or grinding. That way it is possible not only
to
smoothen the surface of the formed profile or the formed ledge but also to
structure
or if necessary to deburr said surface.
Fig. 4 shows the further advancement of the production of the profile or the
ledge
21. If for forming the ribs or crossbeams 21a in the profile or ledge 21
locally more
molding compound is to be applied, the process pressure is increased
accordingly
by the closed loop control of the injection process. The closed loop control
and
control, respectively, of the movement of the carriage 10 relative to the mold
insert is
done by the machine control unit. There the injection parameters relevant for
the
process (pressure, temperatures, process times, strokes) are controlled
depending
on the relative movement of the carriage 10.
Fig 5 shows a process stage during the formation of the profile or ledge 21
shortly
before the molding compound fills the second end section of the cavity 4. Fig
6.
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shows the last stage of the filling of the cavity 4 with filling up the recess
12b in the
carriage insert 11, that way the second end cap of the profile or ledge being
generated. As at a conventional injection molding process a holding pressure
is kept
up for a defined period in order to support or assure the proper forming of
the profile
or ledge at the designated end of the part.
Subsequently the profile or ledge 21 is cooled in the carriage insert 11 for a
certain
period of time in order to assure its solidification. The mold is opened and
the profile
or the ledge 21 is ejected by an ejector system 19 as state of the art at
conventional
injection molds.
At the embodiment of the invention shown in the figures the carriage 10 is
translated
relatively to the mold insert 1. It also is possible to position the profiled
mold insert 1
at a fixed and not movable part of the mold and to translate the mold insert
1at the
nozzle side of the mold together with the injection unit 6 relatively to the
mold insert.
Carriage and carriage insert can be designed as one single part, while a
design with
a mold insert offers the advantage of interchangeability of the insert. The
carriage
can be designed segmented or as a multi part carriage, wherein components of
the
carriage can be positioned on the upper part of the mold as well as on the
lower part of
the mold. The embodiment of the single components of the mold can also be done
such that no straight, linear movement occurs but the mold insert at the
nozzle side
of the mold is moved along a 3-dimesional path in order to produce constantly
or
irregularly curved profiles or ledges. It is also possible and economically
advantageous to inject into the profiled mold insert during the forward motion
and
during the backward motion of the carriage. This reduces the unoccupied times
and
thus the production cycle times. The injection into several cavities connected
in
series or connected in parallel is also possible.
The injection unit 6 can be equipped with one or more barrel(s), which are
arranged
in series or in parallel. If arranged in series different molding compounds
for the
production of multi-component parts or equal materials, in order to increase
the shot
volume, can be applied. A particularly advantageous mode of operation is the
application of two or three injection cylinders that operate in an alternating
or in a
cyclic mode. There one injection cylinder injects molding compound into the
mold
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while in the other cyclinder(s) new molding compound is plasticized. At
unequally
distributed injection and metering times three cyclinders can be of advantage.
If
several cyclinders are applied the melt streams are joined in a nozzle with
control
valve. The control of the injection process is preferably done depending on
the
5 injection pressure also a time or stroke dependent process control is
possible. The
operation mode with alternating injection units enables the production of very
long
profiles or ledges with high volumes with small injection units. Thus due to
the low
clamp force demand the machines can be built very small, also small aggregates
can be applied for production cells in accordance with the invention.
The rheological layout of the process and the mold, respectively, is
preferably done
with simulation software. This could be enhanced software packages based on
programs that are typically applied for injection molding process simulation.
The
development of customized program modules can be considered as beneficial for
the simulation of the process in accordance with the invention.
In analogy to the process and the mold known from WO 2006/045720 the design of
the mold can also comprise a core in order to be able to manufacture special
part
geometries.
As molding compound for the process in accordance with the invention mainly a
thermoplastic material is to be considered which in molten condition is
injected into
the mold under temporarily defined influence of pressure and temperature and
which solidifies in the mold due to freezing of the molten material. The
molding
compound can also be a reactive liquid, exemplarily a thermoset or an
elastomer,
which can be injected into the mold in analogy to a thermoplastic material but
which
solidifies due to chemical reaction. Thermoplastic molding compounds can be
reinforced with fibers, for example with glass fibers. The process pressure at
the
injection process corresponds to levels customary to the pressure levels at
conventional injection molding. Also inlay-parts or inserts made out of other
materials such as glass, metals, composites or wood can be applied for the
production of hybrid profiles or ledges. There the inserts are overmolded when
the
molding compound is continuously injected and a positive fit connection with
said
inlays is established. By the application of decorative films, textiles and
veneers as
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cavity inlays components with decorated surface can be produced with the
process
according to the invention.
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REFERENCE NUMERALS
1 .. Mold Insert
2 ....... Hot runner nozzle
3 ....... Gating insert
3a ...... Outer surface
4 ....... Mold cavity
4a .. Closed end section
4b ...... Open end section
4c ...... Closed end section
5 ....... Recess
6 ....... Injection unit
7 .. Tempering element
7a ...... Outer surface
7b ...... Heated part
7c ...... Opening
7d ...... Cooled part
9 .. Heating element
10 ...... Carriage
10a ..... Recess
11 ...... Carriage insert
11a ..... Jaws
12a .. Recess
12b ..... Recess
12c ..... Hollow section / void
12d ..... Recess
17 ...... After-treatment unit
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18 ...... Sliding element
19 ...... Ejector unit
20 ...... Molding compound
20a ..... Melt front
21 .. Profile
21a ..... Cross beams
22 ...... Drilling
